/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.condition;

import java.util.Collection;
import java.util.Iterator;

/**RequestMapping注解的每个属性条件的抽象
 * <br/>A base class for {@link RequestCondition} types providing implementations of
 * {@link #equals(Object)}, {@link #hashCode()}, and {@link #toString()}.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public abstract class AbstractRequestCondition<T extends AbstractRequestCondition<T>> implements RequestCondition<T> {

	/**判断条件是否为空，即根据条件内容是否为空进行判断
	 * <br/>Indicates whether this condition is empty, i.e. whether or not it contains any discrete items.
	 * @return {@code true} if empty; {@code false} otherwise
	 */
	public boolean isEmpty() {
		return getContent().isEmpty();
	}

	/**获取本条件的内容，对于任意具体的属性条件来说，该方法返回注解中属性对应的值，把数组转换为Collection
	 * <br/>Return the discrete items a request condition is composed of.
	 * <p>For example URL patterns, HTTP request methods, param expressions, etc.
	 * @return a collection of objects (never {@code null})
	 */
	protected abstract Collection<?> getContent();

	/**执行toString方法时，内容中多个值的分隔符，可以是"||"或者"&&"
	 * <br/>由此可知，每种条件中的内容之间可以是"或"的关系，也可以是"与"的关系
	 * <br/>The notation to use when printing discrete items of content.
	 * <p>For example {@code " || "} for URL patterns or {@code " && "}
	 * for param expressions.
	 */
	protected abstract String getToStringInfix();

	// 判断条件是否相等，需要的内容是相同的。子类的Content有可能是Set，也有可能是List，具体看属性特性
	@Override
	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (other == null || getClass() != other.getClass()) {
			return false;
		}
		return getContent().equals(((AbstractRequestCondition<?>) other).getContent());
	}

	@Override
	public int hashCode() {
		return getContent().hashCode();
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder("[");
		for (Iterator<?> iterator = getContent().iterator(); iterator.hasNext();) {
			Object expression = iterator.next();
			builder.append(expression.toString());
			if (iterator.hasNext()) {
				builder.append(getToStringInfix());
			}
		}
		builder.append("]");
		return builder.toString();
	}

}
